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(CNN)For Donald Trump, winning the state of Pennsylvania is an uphill fight.

But if he takes the Keystone State, it likely comes with the keys to 1600 Pennsylvania Avenue.

"There are 800,000 more active Democrats than Republicans here," said Terry Madonna, director of the Franklin Marshall College Poll and the sage of Pennsylvania politics. "The fact of the matter is Donald Trump does have a tough battle. I'm not saying he can't win, but I'll tell you what, if he did, the presidential race is over."

The latest Muhlenberg College/Morning Call poll has Clinton with a comfortable 9-point lead over Trump but Madonna says the race is likely much closer.

"This election, his average in polls, has not been 5% or below for four months. And that's huge," he said.

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Trump and his running mate, Indiana Gov. Mike Pence, have returned to the state often -- nine visits between the two of them so far, with more on the way.

The campaign has also started to advertise in the state. After spending a sum total of zero on TV advertising through August, Trump has now spent nearly $3 million dollars on an advertisement highlighting immigration and security concerns.

Clinton, meanwhile, is taking no chances. Her campaign opened its 55th office in the state this week, she currently has more than 300 campaign organizers -- and expects many more by Election Day -- and she and her running mate, Virginia Sen. Tim Kaine, have been here 11 times, not including the party's convention, which was held in Philadelphia. Clinton has also spent four times that of Trump, around $12 million, on TV advertising in Pennsylvania.

Trump has made a play for Pennsylvania based on broad support in the rural and western areas of the state. But he needs to compete in Philadelphia and the surrounding suburbs, where a third of the states' voters live, if he hopes to turn the state red.

"If he loses the Philly suburbs by a few thousand voters, then fine," Madonna said, "but he can't lose by six figures. He won't be able to make up the difference."

Both campaigns have descended on Philadelphia and the surrounding counties to register voters and motivate them to vote. Hoping to appeal to women and moderates, Trump announced his childcare initiative in Aston just west of Philadelphia.

In the same week, President Barack Obama, Clinton's strongest surrogate, made his first solo campaign appearance for her in Philadelphia trying to motivate young and African-American voters.

Philadelphia and the surrounding areas cannot be underestimated. In 2012, Mitt Romney won 54 of Pennsylvania's 67 counties but still lost the state to Obama by 5.5% because of the heavy Democratic turnout in Philadelphia, the surrounding counties and the other Democratic stronghold, Pittsburgh.

Though a Republican presidential candidate hasn't won Pennsylvania since 1988, it is often a battleground because most presidential contests here were won by 5 or 6 points. Obama's 10-point advantage in 2008 was a blowout.

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Voter registration across state was strong in July and August, actually running ahead of registration efforts in 2008, which was a banner year. Democrats have registered some 418,000 voters so far this year to Republicans' 321,000.

With the last day to register, October 11, looming, both camps have moved into high-gear to find new voters.

At a recent GOP get-out-the-vote effort in Stroudsburg, volunteers fanned out through neighborhoods looking for votes with instructions to be friendly and under no circumstances to engage in arguments with Clinton supporters.

Clinton launched a broad effort this week to get younger voters engaged. She spoke to a small group of students at Temple University, promising progress on a host of issues from student loans to job to climate change.

"If I'm in the White House," Clinton said to great applause, "young people will always have a seat at any table where any decision is being made."

Pennsylvania will be a test for Clinton's enormous campaign operation versus the enthusiasm of Trumps' most ardent supporters. With no early voting in the Keystone State, the race here will go all the way to November 8.